How to send an untraceable message from a burner account to let someone know their spouse is cheating

I need to tell someone their spouse is cheating. Obviously I know I need to create a burner account as I don't want blowback on me but I worry they'll be able to trace the IP number and identify me. From what I've seen I should get a burner phone, use public wifi and use a VPN. Would the person still know my approximate geographic location? That would be a huge giveaway if they saw my city.